Common blood protein protects patients from lethal ‘black fungus’ infection, new study finds

Representative fluorescence microscopy images from three independent experiments showing CFW-labeled R. delemar spores cultured for 6 h in the presence of FITC-labeled albumin, performed in duplicate. Credit: Nature (2026). DOI: 10.1038/s41586-025-09882-3

Albumin is the most common protein in the blood, a vital molecule produced by the liver that helps maintain fluid balance and transports proteins and hormones. It also plays a key role in fighting off a lethal disease called mucormycosis or “black fungus,” according to a new study published in Nature. This is the first time the protein has been shown to have a direct role in helping the body defend against a fungal pathogen.

Deadly infection

Mucormycosis is a rare and severe fungal infection that can spread to many parts of the body. It typically affects people with diabetes and weakened immune systems and acts like an invasive weed growing into blood vessels and killing tissue. More than 50% people diagnosed with mucormycosis do not survive.

To understand why this specific fungus targets people with metabolic issues, the researchers looked at clinical data from hundreds of patients. They suspected that albumin might be involved because they noticed that patients who died from the infection almost always had very low levels of this protein. Previous research had also linked low albumin levels to lower survival rates in patients fighting a number of other infections.

To confirm whether normal levels of albumin provide protection, the team conducted lab experiments where they removed the protein from healthy blood. When they added the fungus to these samples, it grew out of control. And when the albumin was restored, it stopped the pathogen in its tracks.

The scientists then examined how the protein could do this and discovered that albumin has pockets that bind fatty acids. When albumin encounters the fungus, it releases these protective fats, which prevent it from producing mucoricin, a toxin that kills human tissue.

Albumin deficiency compromises serum FFA composition and increases susceptibility to mucormycosis. Credit: Nature (2026). DOI: 10.1038/s41586-025-09882-3

New help for patients

The discovery could give doctors new ways to detect, treat and fight the fungal disease. As senior author Georgios Chamilos notes in the paper, “Our findings reveal a master regulatory role of albumin in host defense against Mucorales [the order of fungi that includes several species that can cause mucormycosis], suggesting that correcting hypoalbuminemia could be a simple and effective strategy to prevent and treat mucormycosis.”

For example, developing a simple test for albumin levels could act as an early warning system to identify people at risk. In terms of treating patients, the research may serve as a basis for the design and development of new targeted therapies. But, more straightforward and practicable in the short term, could be giving at-risk individuals albumin supplements to restore their natural defenses.

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Scientists discover blood protein albumin transforms harmless fungus into dangerous pathogens